Traveling wave tube apparatus



W. R. 'AYERS May 2 w67 TRAVELING WAVE TUBE APPARATUS Filed June 25 INVENTOR. WALTER R. AY ERS ATTORNEY United States Patent O 3,317,780 TRAVELING WAVE TUBE APPARATUS Walter Revis Ayers, Sunnyvale, Calif., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed June 25, 1962, Ser. No. 204,952 8 Claims. (Cl. S15- 3.5)

The present invention relates in general to electron devices and, more particularly, to apparatus for eflicient assembly and cooling of traveling-wave tubes.

In electron devices such as traveling-wave tubes it becomes necessary to cool certain portions of the tube. Typically, in traveling-wave tubes heat is generated in the collector electrode where the electron beam is collected and in the slow-wave structure where a certain portion of the beam is intercepted. In prior art, traveling-wave tubes producing low powers, it has been sufficient to allow the tube body housing the slow-wave structure to run hot. In traveling-wave tubes of higher powers of the type described herein it is necessary for proper operation of the tube to cool the body as well as the collector.

Also, in systems recently designed to utilize an array of traveling-wave tubes mounted together it is desirable to have each tube and its associated focusing magnet assembly mounted in such a manner whereby it can be slideably removed from the array for repair or replacement.

According to the present invention a high thermal conductance path is provided from the slow-wave structure or circuit of the traveling-wave tube to the tube body and the body is iluid cooled by means of the same coolant fluid used to cool the collector. Also, by means of a saddle on the output coupling of the tube the circuit can be inserted in the tubular body portion of the tube after the output window and coupling assembly has been sealed into the body portion of the tube, and a tube body cooling sleeve which serves as the inner mount for a stack of permanent magnets is provided into which the assembled tube cau be inserted and sealed from one end thereof, the sleeve serving as the outside wall for a cooling chamber adapted for cooling the tube body.

The-principal object of the present invention is to provide novel apparatus for efficient construction and cooling hot elements of a traveling-wave tube.

One feature of the present invention is the provision of a novel traveling-wave tube provided with a high thermal conductance path from the slow-wave structure of the tube to the tube body by means of grooves provided in the outside diameter of the slow-wave structure and the inside diameter of the tubular body adapted to receive and contact a support rod whereby good thermal contact is provided between the slow-wave structure, said support rod, and said tubular body for conducting heat from the slow-Wave structure.

Another feature of the present invention is the provision of a novel traveling-wave tube provided with means for cooling the tube body coupled to the means for cooling the collector of the traveling-wave tube.

Still another feature of the present invention is the provision of a novel coupling assembly to the slow-wave structure of a traveling-wave tube including a saddle on an outwardly directed pin sealed in the output window of the tube whereby the slow-wave structure can be inserted in the tubular body portion of the tube and joined to the output coupling after the output window and pin have been sealed in the body portion of the tube.

Still another feature of the present invention is the provision of a novel traveling-wave tube body cooling system including a tube body cooling sleeve which serves as the inner mount for a stack of permanent magnets slideably mounted thereon, the sleeve serving as the outside 3,3 l 7,780I Patented May 2, 1967 ICC wall for the cooling chamber adapted for cooling the tubular body portion of the tube.

These and other features of the present invention will become more apparent upon a perusal of the following specification taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a fore-shortened side cross-sectional view of a traveling-wave tube embodying features of the present invention,

FIG. 2 is an enlarged cross-sectional view of a portion of the structure of FIG. 1 taken along the line 2 2 in the direction of the arrows,

FIG. 3 is an enlarged elevational view, partially tbroken away, of that portion of the structure shown in FIG. 1 delineated by the line 3-3, and

FIG. 4 is an enlarged cross-sectional View of the portion of the structure shown in FIG. 1 taken along line 4-4 in the direction of the arrows.

Referring now to FIG. 1 of the drawing, a travelingtube amplifier 11 includes an evacuated envelope 12 at one end of which is positioned an electron gun structure 13 including a cathode assembly 14 and associated cylindrical anode 15 adapted for generating a beam of electrons. Positioned at the other end of the evacuated envelope 12 is a collector electrode structure 16 adapted to receive the electron beam generated by the electron gun structure 13.

Between the electron gun structure 13 and the collector electrode structure 16 a tubular main body portion 17 of the evacuated envelope 12 houses a slow-wave structure shown, for example, as a ring and bar type of contrawound helix 18 of, for example, molydbdenum mounted on a plurality of dielectric support rods 19 of, for example, sapphire which are fitted within the envelope 12 in a manner described in greater detail below with respect to FIG. 2.

The slow-wave structure 18 is severed in several places along its length and connected to ring-like drift members 20 to provide greater stability and to prevent R.F. feed- Ithrough in the tube when the beam is turned oif and the R.F. is still on. The inside diameter of the tubular main body portion 17 and the outside diameter of the tubular slow-wave structure 18 are provided with groove portions 21 and 22 semicircular in cross-section, respectively, in which the support rods 19 are adapted to seat. grooves 21 and 22 are of the same radius a's the support rods 19 so that the support rods 19 contact both the tubular slow-wave structure 18 and the main body portion 17 of the evacuated envelope 12 over a large surface for conducting heat from the slow-wave structure 18 through the support rods 19 to the main body portion of the evacuated envelope. The outside diameter of the drift members 20 is cut away so that these drift members 20 slideably t within the main body portion 17 of the limited amount of heat could be conducted from the cir- 4 cuit through the rods to the envelope. According to the structure of the present invention much b etter heat conduction is provided from the circuit to the envelope thereby permitting construction of higher power tubes.

A radio frequency energy input coupling means 23 is K provided at the gun end of the envelope 12 for applying a radio frequency wave to the slow-wave structure 18. The input coupling means 23 includes a pin 24 of, for

These i example, Monel projecting radially inwardly from the evacuated envelope and which has a hollow tip into which lits a pin 25 of, for example, Monel fixedly secured to the end of the slow-wave structure 18.

A radio frequency output coupling means 26 is provided at the collector end of the main body portion 17 for extracting an amplified radio frequency wave from the slow-wave structure 18. The output coupling means 26 includes a wave permeable window 27 of, for example, alumina ceramic sealed in the main body portion 17 in a vacuum tight manner and provided with a central pin 28 of, for example, Monel sealed therein and projecting therethrough radially inwardly t-oward the slow-wave structure 18. Externally of the vacuum envelope the pin 28 is adapted to connect the center conductor of a coaxial line (not shown). Within the evacuated envelope a saddle member 29 of, for example, Monel provided with a hole to receive the pin 28 is lixedly secured as by brazing to the slow-wave structure 18 and to the pin 28.

A periodic magnetic eld is provided longitudinally of the tube axis by means of annular permanent magnets 34 and pole pieces 35 positioned therebetween for focusing the electron beam of the tube.

The magnets and pole pieces are contained between anv inner hollow cylindrical metallic sleeve member 32 of, for example, stainless steel and an outer hollow metallic sleeve member 33 of, for example, steel. The inner sleeve member 32 surrounds the main body portion 17 of the tube, the anode end of the inner sleeve 32 abutting a radially outwardly projecting portion of the anode. The end of the inner sleeve 32 adjacent the collector 16 is held in place by a knurled ring 36 which threads onto threads on the collector, centers the inner sleeve 32 about the main body portion 17 and forces the inner sleeve 32 longitudinally against the anode 15 at the gun end of the tube.

Apertures are provided in the inner sleeve 32 to pass the input and output coupling means 23 and 26, respectively, and the output coupling means 26 terminates ush with the outer surface of the inner sleeve 32 whereby the magnets 34 and pole pieces 35 can be slid onto the inner sleeve 32 `after the inner sleeve 32 has been mounted on the tube or alternatively will permit the entire magnet assembly and inner sleeve to be mounted on the tube body as a single sub-assembly. A knurled ring 37 threads onto threads on the outside surface of the inner sleeve 32 for forcing the magnets 34 and pole pieces 35 against the anode 15. The input coupling means 23 terminates inside the outer sleeve 33 and `apertures are provided in the outer sleeve 33 and in the magnet stack for connecting coaxial line means to the input and output coupling means 23 and 26.

The collector electrode structure 16 comprises a hollow cylindrical block 41 of, for example, copper provided with a plug 42 in the bore thereof for preventing passage of electrons entirely through the collector. The outside surface of the block 41 is provided with an input coolant fluid helical passageway 43 and an output coolant fluid helical passageway 44 which are arranged in the form of a double helix, the helical passageways 43 and 44 connecting with inlet and outlet coolant fluid tubes 45 and 46, respectively. The tubes 45 and 46 project axially from the end of the collector. A collector sleeve 47 surrounds the cylindrical block 41 and is sealed thereto in a uid tight manner to make the passageways 43 and 44 uid tight.

A body cooling fluid chamber 51 is defined between the inner magnet assembly sleeve 32 and the tubular main body portion 17 longitudinally of the tube from the inner end of the ring 36 in the region surrounding the collector 16 to a ring 52 surrounding the main body portion 17 and through which the input coupling means 23 passes at the Ianode end of the tube. Sealing means such as rubber O-rings 53 are provided at the ends of the body cooling ud chamber 51 as well as an O-ring 54 around the output coupling assembly 26 which passes through the chamber 51. The cooling fluid chamber 51 is divided in half into two passageways by two longitudinal metallic rods 55 of, for example, stainless steel which are secured 1n place as -by brazing either to the main body portion 17 of the tube or to the inside wall of the inner sleeve 32 and which extend from the collector end of the chamber 51 to adjacent the ring 52 at the anode end of the charnber 51. One half of the chamber 51 is connected to the input coolant fluid passageway 43 via .a hole 56 and the other half of the chamber 51 is connected to the output coolant fluid passageway 44 via another hole 57.

Thus the chamber 51 is formed into an elongated passageway whereby coolant fluid coming in the inlet tube 45 passes down the input helical passageway 43, into one side of the chamber 51 via the hole 56, down the length of the tube, around to the other side of the tube adjacent the ring 52, back down the tube toward the collector, into the output helical passageway 44 via the hole 57, and out the outlet coolant fluid tube 46. The construction of the cooling assembly provides a good collector and body cooling system which has both its inlet and outlet at the collector end of the tube parallel to the axis of the tube whereby lthe tube can be mounted in a phased array and easily removed therefrom by merely withdrawing the R.F. coaxial line connections thereto and uncoupling the fluid tubes 45 and 46.

Also, by removing the knurled ring 36 the tube itself can be removed from the magnet stack for replacement or for repair of its fluid cooling system without opening the vacuum envelope of the tube and without disassembling the magnet stack sub-assembly.

The tube is assembled in the following manner. The anode assembly 15, input coupling means 23 without the pin 24, and the -output coupling means 26 are assembled to the main body portion 17. The slow-wave structure is inserted in the tube until the pin 25 matches up to the position where pin 24 will contact it. Then the pin 24 is connected to the pin 25 and the input coupling 23 sealed. The saddle 29 is secured to the slow-wave circuit 18 and then xedly secured to the pin 28 as by spot welding. The collector 16 is slid onto the main body portion 17 and sealed thereto as by induction brazing. The gun is then inserted in the cathode housing and the tube is evacuated and processed.

The inner sleeve 3-2 is provided on the assembled tube by first placing the O ring 53 at the anode end of the tube and the O ring 54 around the output coupling assembly 26. The sleeve 32 is slid longitudinally of the tube to abut the anode at which point it will drop over the output coupling 26 and seat upon the O ring 54. Then the other O ring 53 is inserted in the collector end of the sleeve V32 and the sleeve 32 secured in place by screwing the ring 36 onto the collector 16.

A typical pulsed traveling-wave tube constructed in the manner described operates over a frequency range of from 1.254 to 11386 ge. with peak powers of about 5 kw., a noise figure of about `30 db and gain of 50 db.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A fluid-cooled traveling-wave tube comprising, in combination,

(a) a cathode,

(b) an anode,

(c) a collector electrode,

(d) means interposed between said anode and said collector electrode for producing interaction between a radio frequency wave and an electron beam traveling from said cathode to said collector,

(e) a `tubular body portion surrounding said means for producing interaction,

(f) said collector electrode provided with cooling fluid passageways,

(g) a tubular body cooling sleeve surrounding said tubular body portion,

(h) means for closing the ends of said body cooling sleeve about said body portion to provide a chamber surrounding said body portion,

(i) means for connecting said chamber surrounding said body portion with said cooling uid passageways of said collector electrode,

(j) means for passing cooling fluid to and from said chamber and said passageways of said collector for cooling said tube, and

(k) radio frequency coupling means for transferring electromagnetic energy between said interaction means of said tube and externally of said tubular body cooling sleeve which surrounds said tubular body portion, said radio frequency coupling means being electrically isolated from cooling fluid present in said chamber.

2. The traveling-wave tube of claim 1 wherein said radio frequency coupling means is an output radio frequency coupling means sealed in said tubular body portion and connected to said means for producing interaction, said coupling means projecting through said chamber and said tubular body cooling sleeve and means for creating a fluid tight seal between said coupling means and said tubular body cooling sleeve.

3. A fluid cooled traveling-wave tube comprising, in combination,

(a) a cathode,

(b) an anode,

(c) a collector electrode,

(d) means interposed between said anode and said collector electrode for producing interaction between a radio frequency wave and an electron beam traveling from said cathode to said collector electrode,

(e) a tubular body portion surrounding said means for producing interaction,

(f) inlet and outlet cooling fluid tubes,

(g) said collector electrode provided with double helical cooling uid passageways,

(1) the rst of said helical passageways connected to said inlet tube, and

(2) the second of said helical passageways connected to said outlet tube,

(3) a collector sleeve disposed about said rst and second helical passageways in a uid tight manner, said collector sleeve forming an extension of said tubular body portion surrounding said means for producing interaction, said collector sleeve having a pair of apertures therein for coupling ytluid between thel inner and outer surfaces of said collector sleeve,

(h) a tubular body cooling sleeve surrounding said tubular body portion,

(l) means for closing the ends of said body cooling sleeve about said body portion to provide a chamber surrounding said body portion and (2) means for dividing said chamber into a pair of elongated passageways, and l (i) one of said apertures in said collector sleeve providing uid coupling between one end of one of said pair of elongated passageways and said rst helical passageway, and the other of said apertures in said collector sleeve providing fluid coupling between one end of the other of said pair of elongated passageways and said second helical passageway.

4. A radio frequency coupling connection for coupling to the slow-wave circuit within and spaced from the body portion of a traveling wave tube including,

(a) a wave permeable window assembly sealed in the body portion of said tube,

(b) a pin projecting through said window assembly radially inwardly of said body envelope toward the slow-wave circuit,

(c) a curved saddle shaped conductive member coupled to said pin and xedly secured to the exterior peripheral surface of said slow-wave circuit, said saddle shaped conductive member having an internal surface curvature corresponding to the exterior surface curvature of said slow-wave circuit.

5. A traveling wave tube comprising, in combination,

(a) a cathode,

(b) an anode,

(c) a collector electrode,

(d) a metal tubular body portion positioned between said anode and said collector electrode,

(e) a tubular slow-wave structure positioned within said tubular body portion and adapted to propagate a traveling electromagnetic wave for interaction with the electron beam produced between said cathode and said collector, and

(f) support rods supporting said slow-wave structure concentrically within and spaced from said tubular body portion,

(g) the inside diameter of said tubular body portion being provided with elongated longitudinally extending grooves to receive said support rods whereby good thermal contact is made between said slowwave structure, said support rods and said tubular body portion for conducting heat from said slowwave structure.

6. A uid cooled magnetically focused traveling wave tube comprising in combination, an electron gun, a co1- lector structure, and a slow-wave circuit disposed between and coupled to said electron gun and said collector, a tubular body portion surrounding said slow-wave circuit, said collector structure being provided with bidirectional cooling fluid passageways, a tubular body cooling sleeve surrounding said tubular body portion and spaced therefrom along the longitudinal axis of said tubular body portion, means for closing the end portions of said body cooling sleeve about said body portion to provide a charnber surrounding said body portions, means for connecting said chamber surrounding said body portion with said cooling uid passageways of said collector structure, magnetic focusing means surrounding said tubular body cooling sleeve, said cooling chamber being provided with means for providing bidirectional Huid How through said chamber along the longitudinal axis of said chamber, the bidirectional uid passageways of said collector and said chamber being interrelated such that cooling uid coupled into one of said bidirectionalcooling fluid passage-` ways of said collector passes into said chamber surrounding said body portion passes along the length of said chamber and then reverses its ow path at the other end of said chamber and again passes along the length of said chamber and into said other of said bidirectional cooling duid passageways of said collector.

7. The traveling wave tube defined in claim 5 including elongated longitudinally extending grooves provided in the outside diameter of said slow-wave circuit along the longitudinal extent thereof, said support rods being in contact with said slow-wave circuit in said grooved portions thereof.

8. A fluid cooled traveling wave tube comprising in combination, an electron gun, collector structure, slowwave circuit means disposed between said electron gun and said collector structure, a metallic tubing disposed around said slow-wave circuit and electrically insulated therefrom, a tubular body cooling sleeve spaced from and surrounding said metallic tubing to form a cooling chamber therebetween, and magnetic focusing means surrounding said tubular body cooling sleeve, tluid coupling means coupled to said collector structure, said collector structure having bidirectional fluid cooling passageways, fluid coupling means for coupling Huid between said cooling chamber and said bidirectional uid cooling passageways in said collector structure, said traveling wave tube being 2,970,240 1/ 1961 Iversen B15- 3.5 further provided with radio frequency coupling means 2,993,143 7/1961 Kelliber et a1 3dS-36 for transferring electromagnetic energy between said slow- 3,051,866 8/1962 Nason 315-538 X wave circuit and externally of said tubular body cooling 3,070,725 17d/1962 Lee et aL 315 3.5 sleeve, said radio frequency coupling means being electri- 5 cally isolated. from cooling fluid flowing through said fluid 3211947 10/1965 Bloom 313 17 Coolmg PQIUOHS 0f Sald tube- HERMAN KARL SAALBACH, Primary Examiner.

References Cited by the Examiner UNITED STATES PATENTS 2,801,360 7/1957 Robertson et al. 3dS-3.5 2,806,171 9/1957 Iversen 3153.5

ARTHUR GAUSS, Examiner.

10 S. CHATMON, JR., Aassstant Examinar. 

1. A FLUID-COOLED TRAVELING-WAVE TUBE COMPRISING, IN COMBINATION, (A) A CATHODE, (B) AN ANODE, (C) A COLLECTOR ELECTRODE, (D) MEANS INTERPOSED BETWEEN SAID ANODE AND SAID COLLECTOR ELECTRODE FOR PRODUCING INTERACTION BETWEEN A RADIO FREQUENCY WAVE AND AN ELECTRON BEAM TRAVELING FROM SAID CATHODE TO SAID COLLECTOR, (E) A TUBULAR BODY PORTION SURROUNDING SAID MEANS FOR PRODUCING INTERACTION, (F) SAID COLLECTOR ELECTRODE PROVIDED WITH COOLING FLUID PASSAGEWAYS, (G) A TUBULAR BODY COOLING SLEEVE SURROUNDING SAID TUBULAR BODY PORTION, (H) MEANS FOR CLOSING THE ENDS OF SAID BODY COOLING SLEEVE ABOUT SAID BODY PORTION TO PROVIDE A CHAMBER SURROUNDING SAID BODY PORTION, 